Normally, MRI uses a radio wave (hereinafter, RF) and a gradient magnetic field to selectively excite an arbitrary plane with a thickness in a one-dimensional direction. Also, there is a two-dimensional spatial selective excitation (spectral-spatial; hereinafter, referred to as SS) method of identifying two directions and selectively exciting only the inside of a region limited by the two directions. In the two-dimensional spatial selective excitation method, an RF pulse is applied in addition to an oscillating gradient magnetic field pulse. At this time, the RF pulse applied in addition to the oscillating gradient magnetic field pulse is referred to as a two-dimensional selective excitation pulse (2D RF pulse). Also, a pair of the 2D RF pulse and the oscillating gradient magnetic field pulse is referred to as a two-dimensional spatial selective excitation pulse.
On the contrary to this, there is a method of selectively exciting a three-dimensional space by applying a two-dimensional spatial selective excitation pulse multiple times (for example, see Non-Patent Literature 1). This method is referred to as a three-dimensional spatial selective excitation method, a plurality of RF pulses applied at this time are referred to as 3D RF pulses, and pairs of the respective 3D RF pulses and the oscillating gradient magnetic field pulse are referred to as three-dimensional spatial selective excitation pulses. Additionally, hereinafter, these pulses are referred to as a multi-dimensional spatial selective excitation pulse in the present description in a case where there is no need to distinguish between two and three dimensions in particular or a case where the two and three dimensions are included.
In the two-dimensional spatial selective excitation method, an application time of the two-dimensional selective excitation pulse is long; an excitation profile is distorted by various factors, which results in shifting an excitation position easily. The representative factors affecting an excitation profile and an excitation position are a residual magnetic field and an eddy current due to an oscillating gradient magnetic field pulse, an inhomogeneous static magnetic field, timing delay between applications of an oscillating gradient magnetic field pulse and an RF pulse (hereinafter, referred to as “GC Delay”), etc., and an excitation position shift due to these factors is referred to as an excitation position shift due to apparatus distortion in the present description. Also, reducing the excitation position shift due to apparatus distortion is referred to as pulse stabilization.
As the pulse stabilization method, there is a method in which an influence due to a residual magnetic field and an eddy current is corrected using a phase of an excitation profile (for example, see Patent Literature 1). Also, there is a technique for measuring static magnetic field inhomogeneity in a region of interest and correcting the influence (for example, see Patent Literature 2). Additionally, there is a technique for reducing timing delay between applications of an oscillating gradient magnetic field pulse and an RF pulse while changing a coefficient to determine a cylinder diameter in an excitation region and a time difference to determine an offset position (for example, see Patent Literature 3).